Wave-particle duality and de Broglie wavelengthEdexcel A-Level Physics: Mind map

Exam questions on Wave-particle duality and de Broglie wavelength

1. Electrons travelling at a speed of 4.0 × 10⁶ m s⁻¹ are directed at a thin crystal in an evacuated tube. The spacing between neighbouring atoms in the crystal is about 2 × 10⁻¹⁰ m. The Planck constant is 6.63 × 10⁻³⁴ J s and the mass of an electron is 9.11 × 10⁻³¹ kg.
   Explain why a beam of these electrons would be expected to show noticeable diffraction at the crystal.2 marks
2. In an electron diffraction tube, electrons are accelerated through a potential difference in a vacuum and directed at a thin film of graphite. They then strike a fluorescent screen, where a pattern of concentric bright rings is seen.
   Explain how the ring pattern shows that electrons have wave properties.2 marks
3. Electrons are released from rest and accelerated through a potential difference of 250 V in a vacuum, then directed at a thin crystal. The electron charge is 1.60 × 10⁻¹⁹ C, the electron mass is 9.11 × 10⁻³¹ kg and the Planck constant is 6.63 × 10⁻³⁴ J s.
   Calculate the speed of the electrons after acceleration.3 marks